1. Technical Field
The present invention relates to toner recovery devices for imaging apparatus--in particular, to a toner recovery device for an imaging apparatus that forms toner images on the circumferential surface of a photoconductive drum, and by a transfer device transfers the toner image formed on the photoconductive drum circumferential surface onto the face of a sheet.
2. Description of Related Art
With such image-reproducing devices as photocopiers, printers, facsimile devices, a document is loaded on a document plate provided on the upper surface of the device, the document image is irradiated with light, and reading the document image is carried out based upon the light reflected from the document. Based upon the read image, an electrostatic latent image is formed on the surface of the photoconductive drum. The photoconductive drum is charged to a predetermined polarity by a main charger, and is irradiated with light from an exposure means to remove the charge in those portions in accordance with the document image, forming an electrostatic latent image.
The main charger, the exposure means, the developing device, the transfer device, a separation device, and a cleaning unit are disposed surrounding the photoconductive drum.
Toner charged to have the same polarity as the photoconductive drum is stored inside the developing device. In a position contiguous with the developing device and the photoconductive drum, the toner stored within the developing device is adsorbed to the uncharged portions of the photoconductive drum. Consequently, the electrostatic latent image formed on the circumferential surface of the photoconductive drum is rendered visible into a toner image.
Onto a sheet conveyed in between the transfer device and the photoconductive drum, the transfer device through the back surface of the sheet applies a voltage having a reverse polarity to that of the toner, which attracts the toner on the photoconductive drum circumferential surface onto the sheet, transferring the toner image.
The separation device is disposed on the downstream end of the transfer device in the sheet conveyance direction. A separation needle that applies a predetermined voltage may be employed as the separation device, which, so that the sheet does not wind round on the photoconductive drum, is for drawing off the sheet from the backside.
The cleaning unit, which is for removing toner residual on the photoconductive drum circumferential surface, is provided with: a cleaning blade that is brought into contact with the photoconductive drum circumferential surface for scraping off toner; a fur brush for weakening the binding force of the toner on the photoconductive drum circumferential surface; and a toner conveying device that conveys toner stripped from the photoconductive drum circumferential surface to a collector. Installing a toner recovery case within the imaging apparatus and conveying toner removed from the photoconductive drum circumferential surface to the toner recovery case has been suggested. Further, recycling recovered toner by conveying it directly to the developing device and the toner cartridge has also been proposed. In either case, a rotary body termed a "spiral," fitted with screw-shaped wings within a conveyance container configured into a tubular shape is provided, and by rotating the spiral, toner is recovered by conveying it from the cleaning unit to the collector.
Sheet-conveying paths in imaging apparatus are for the most part established in the horizontal direction, in which case the transfer device is set positioned beneath the photoconductive drum. This entails arranging the main charger and the exposure means above the photoconductive drum, and disposing the developing device laterally of the photoconductive drum, and the cleaning unit to the side of the photoconductive drum, opposing the developing device. Consequently, wherein recovery is by directly conveying recovered toner from the cleaning unit to the developing device, the conveyance container will be disposed in roughly the horizontal direction. Herein, toner not conveyed smoothly within the conveyance container risks congesting, and if toner congestion progresses, there is the risk that a so-called spiral lock situation, in which the rotary-driven spiral is halted, will arise. If this situation continues further, toner recovered by the cleaning unit will overflow from inside the conveyance container and the cleaning unit, meanwhile scattering within the apparatus, which puts it out of working order by damaging components for example.